Temperature control system



Sept. 14, 1937. R. P. DEWEY 2,092,753

" TEMPERATURE CONTROL SYSTEM 7 Filed Nov. 11, 1932 no i, OW

z II I k J 3 fl I A :INVENTOR 4 F B73Ltchie P Dewey T W/M Mm 0-L1-E I ATTORNEYS Patented Sept. 14, 1937 TEIVIPERATURE CONTROL SYSTEM Ritchie P. Dewey, Rockford, Ill., assignor to Howard D. Colman, Rockford, Ill.

Application November 11, 1932, Serial No. 642,182

I 3 Claims. (Cl. 236-91) This invention relates generally to temperature control in systems for heating, cooling or ventilating space within a building and more par-- ticularly to a system in which the medium whose temperature is to be regulated is maintained at different predetermined temperatures under thermostatic control according to temperature changes in a controlling medium such as the air outside of the building.

of the shading ring induction type having a main winding Ill constantly excited by alternating current and pairs of multiple turn shading coils II and I2 adapted to be short-circuited selectively to initiate rotation in one direction or the other and movement of the damper toward closed and open positions respectively.

The present invention contemplates control L the circuits for the motor windings by one of at least two independently operable thermostats I3 22 are onnected by conductors 28, 29 and 1 The primary object of the present invention set to respond to difierent predetermined temis to provide a novel inexpensive and reliable p tllres 0f e u at d medium and adapted means for carrying out the above result. to be placed in control of the motor one at a time Another object is to provide a novel control according to temperature changes in the controlsystem of the above character wherein the temling medium detected by at least one thermostat perature at which the regulated medium is mainl4. Herein there are four main controlling ther- 5 tained is varied or adjusted automatically in a mostats numbered I3 I3 I3 and I3 and three plurality of increments according to temperature transfer thermostats numbered I 4 I4 and I 4 changes of the controlling medium. The thermostats I3 each comprise a thermo-sen- In the embodiment of the invention selected sitive element I5 positioned within the space for the purpose of illustration and shown in the whose temperature is to be regulated and adapted accompanying drawing, the air outside of the to move a tongue or common switch terminal building to be heated or cooled constitutes the Hi to close switches l I and I8 depending on controlling medium above referred to and the Whether the temperature detected is above or regulated medium is air within a space into which below the value for which the thermostat is set conditioned air is discharged from the outlet t to respond, at which both of the switches I1 and of a duct '2 through which a current of air is I 8 may be open. forced by a power-driven'blower 3. The air en- The thermostats I4 operate to determine whichv tering the duct 2 may be fresh or recirculated or of the thermostats l3 will, at any time, be in both and may be heated or-cooled to the proper active control of the motor and each has a thertemperature by a coil l supplied with heating mo-sensitive element l9 exposed to the controlor refrigerating fluid. Regulation of the temling medium,'that is the air outside of the buildperature of the regulated medium may be efiected ing. One or the other of two switches 2| and in many ways depending on the type of control 22 is thus maintained closed depending on system to which the invention is applied. For whether the controlling medium is above or beexample, the regulation may consist in starting low the temperature for which the thermostat is and stopping an oil burner, opening and closing set to respond. Means such as a magnet 23 havthe draft of a solid fuel burner,'interrupting and ing poles disposed on opposite sides of the therresuming the flow of heating fluid, or varying mostat tongue 24 serves to hold the common conthe proportion in which air currents are mixed. tact of switches 2| and 22 against one or the 40 Herein the regulating device shown by way of other of the stationary switch contacts and illustration is in the form of a damper-5 disposed causes movement between the contacts to occur in a by-passage 8 and acting by movement be- I with a snap-actiont tween closed and open positions to vary the pro- In the illustrative embodiment, the motor is portion of the air which is exposed to the coil controlled by two circuits having a common con- I in passing through the duct 2 and accordingly ductor 24 leading from a terminal common tochanging the temperature within the space whose the pairs of shading coils II and I2 to the comtemperature is to be maintained substantiall mon contact of the switches of the thermostat constant. I 4 The'stationary contacts of the switches 2l In the present "instance, the damper is actuand 21 are joined respectively by conductors 25 ated by electric driving means in the form of a and 25 to the common switch contacts of the motor I connected through speed-reduction gearthermostats I4 and 14 while the stationary coning 8 to a shaft 9 coupled to the damper. Preftact of the switch H is joined by a conductor erably, a reversible 'motor is used for the appli-' 21 to the tongue of the thermostat I3 The cation herein illustrated, the motor shown being stationary contacts of the switches 22 22" and to the tongues of the thermostats I3 l3 and I3 respectively.

The stationary contacts of the switches I! are made electrically common and joined to the insulated terminal of the shading coils II by a conductor 3| having interposed therein a switch 32 held closed by a cam 33 in all positions of the damper shaft 9 except a limit closed position in which the switch is allowed to open. In a similar way the stationary contacts of the switches l8 are connected to the shading coils I2 through a conductor 34 having a switch 35 interposed therewith and maintained closed by a cam 36 except at the limit open position of the damper.

To illustrate the operation of the system above described, let it be assumed that the system is utilized in acombined cooling and ventilating system wherein it is desirable to maintain within the building a temperature which is maintained constant but which is lower than the temperature outside of the building by a predetermined difierential so that as the outside temperature increases, the temperature to be maintained within the building is correspondingly higher. For such an application, refrigerated fluid would be supplied to the coil I and the thermostats i3 I3 I3 and 13* might be set to respond to temperatures of 7'7, 75, '73 and '71 degrees Fahrenheit respectively and the thermostats I4 {4 and I4 set to respond to temperatures of 85, 80 and degrees respectively. Now assume that the temperature outside the building is below 75 degrees. In such a case, all of the switches 2| would be closed as shown in. the drawing and the conductor 24 thereby connected to the tongue of the thermostat I3 and I8 would be in active control of the circuits for the shading coils l I and I2. Under such conditions, closure of the switch I8 when the temperatureof the air to which the thermostat I3 is exposed falls below '71 degrees would shortcircuit the shading coils l2 causing the damper to be advanced toward open position thereby raising the temperature of the air discharged from the outlet 4 and therefore the temperature in the space to be conditioned. In a similar way, the shading coils ll would be short-circuited by closure of the switch I1 in'response to a rise in temperature above 71 degrees and the damper would be moved toward closed position. Thus, the damper 5 is moved back and forth solely under the control of the thermostat I3 to maintaina room temperature of approximately 71 degrees.

Upon arise in the outside temperature above 75 degrees, the thermostat I4 would open the switch M and close the switch 22 thereby withdrawing active control of the motor from the thermostat I3 and transferring such control to the thermostat l3 which would retain such control so long as an outside temperature within the range from 75 to degrees prevails, during which the conditioned air would be maintained at approximately 73 degrees Fahrenheit. An increase in the outside temperature above 80 degrees would result in opening of the thermostat switch 2| and closure of the switch 22 whereupon the control would be transferred to the thermostat I3 Upon a. still further rise in temperature to a point above degrees, the switch 22 of the thermostat I4 would be closed and the motor placed within the control of the thermostat I3 From the foregoing it will be seen that the Thus, the switches l'l' temperature at which the regulated medium is maintained will be adjusted from time to time and in progressive increments'according to the prevailing temperature of the control medium. Such adjustment of the temperature at which the regulating medium is maintained may, as in the system illustrated herein, vary directly with temperature changes of the controlling medium. Or, as would be the case when the system is employed for controlling the temperature of hot water or other heating fluid in accordance with temperature changes outside of a building, the temperature of the regulating medium would be varied inversely proportional to temperature changes of the controlling medium. Both the control thermostats l3 and the adjusting thermostats are of an inexpensive type well known to operate reliably through long periods of service. The number of thermostats in each group is of course determined by the character of regulation required and the Fange of temperatures to be covered. 1

I claim as my invention:

1. A system for maintaining diflerent predetermined temperatures in a regulated medium according to temperature changes in a controlling medium, said system comprising, in combination, a device operable to vary the temperature of said regulated medium, electrically driven means for actuating said device, a thermostat having two switches with an electrical common terminal connected with said driving means and closed respectively when the temperature of said controlling medium rises above and falls below a predetermined value, second and third thermostats responsive to different temperatures of said regulated medium and each having two switches with an electrically common terminal and closed respectively above and below the latter temperatures, conductors connecting the common terminals of said second and third thermostats respectively to said first mentioned switches, and two control circuits for said driving means including said conductors, a conductor connectin the corresponding switches of said second and third thermostats to said driving means and a conductor connecting the other switches of said second and third thermostats to said driving means.

2. A system for maintaining difl'erent predetermined temperatures of a regulated medium in accordance with temperature changes in a controlling medium, said system comprising in combination, a device movable to increase or decrease the temperature of said regulated medium, electric driving means for said device, two thermostats responsive to different temperatures of said regulated medium and each having two switches respectively controlling said driving means to cause movement of said device to increase or decrease the temperature of the regulated medium, an auxiliary thermostat responsive to temperature changes of said controlling medium and having two switches each in series with the switches of one of said first mentioned thermostats, said last mentioned switches being closed selectively depending on whether the temperature of the controlling medium is above or below a predetermined value.

3. A system for maintaining different predetermined temperatures in a regulated medium in accordance with temperature changes in a con-. trolling medium, said system comprising, in combination, a device movable to increase or decrease the temperature of said regulated medium, elec- V I 2,092,758 trically actuated means -controlling the movement of said device, two independently operable thermostats each having switching means respectively.contro1ling said electrically actuated means for causing movement of said device to increase or decrease the temperature of the regulated medium, each of said thermostats having a bimetallic thermo-sensitive element whereby to permit individual selective adjustment of the efm fective control point of each thermostat, an

auxiliary thermostat responsive to temperature changes of said controlling medium and having two switches each in series, relation with the.

RITCHIE P. DEWEY. m 

